The present invention relates to a method and device for preventing a flexible tubular belt from twisting, for use in a tubular belt conveyer.
A tubular belt conveyer comprising a flexible tubular endless belt for conveying and elevating bulk material such as powder, granule, pulverized solid, and amixture thereof which are completely enclosed within the tubular belt 1, in any direction and any height, has already been developed.
In FIGS. 1-3, there is shown one embodiment of such a conventional tubular belt conveyer. A flexible tubular endless belt 1 which is made of a flexible or elastic material such as rubber, somewhat soft plastic material, or the like, and which is normally biased in a tubular form by its own rolling up tendency around its axis, its inner and outer side ends overlapping each other along its length, is stretched between an upper drive roller 2 and a lower roller 3 on which the endless belt is extended or opened in its width direction against its own rolling up tendency, at a standard slope angle, as shown in FIG. 1.
The tubular belt 1 is properly supported by a plurality of support frames 4 which are positioned along angle frame plates 5 at a certain distance between the two rollers 2 and 3 along the travelling path of the belt 1. Each support frame 4 comprises upper and lower chambers 4a and 4b separated by a partition plate 4c, as shown in FIG. 2, through which a moving path 1a and a return path 1b of the belt 1 are passed. In each chamber 4a or 4b of the support frame 4 a plurality of support rollers 6 are arranged radially around and in contact with the tubular belt 1. The support rollers 6 hold and maintain the tubular form of the belt 1.
The belt 1 opened on the lower roller 3 is closed gradually into the tubular form by its own rolling up force while guide rollers 7 and 8 support the bottom and both the sides of the belt 1, as shown in FIG. 3. In this process, bulk material 10 such as powder, granule, pulverized solid, and a mixture thereof, is fed into the belt opened from a hopper 9 situated above the lower roller 3.
The tubular belt 1 now encloses the bulk material 10 completely, while the side ends of the belt 1 overlap each other, is passed through the upper chambers 4a of the support frames 4 along the moving path 1a of the belt 1, while the tubular belt 1 is supported by the support rollers 6 in the upper chambers 4a, as described above. In this process, the side ends overlapped are situated in the top of the belt, and hence there is no danger that the bulk material enclosed in the tubular belt 1 completely is spilt over the belt 1.
Then, the tubular belt 1 is opened gradually near the upper drive roller 2 by a belt opening mechanism (not shown) having the same construction as the belt closing mechanism shown in FIG. 3. The opened belt 1 is turned around the upper drive roller 2, while the bulk material 10 conveyed is discharged from the belt 1 to a receiver 11 positioned in the top end of the belt 1.
Then, the belt 1 is moved downwards along the return path 1b of the belt 1. The belt 1 opened is gradually rounded again to the tubular form by its own rolling up tendency via a guide roller. The empty tubular belt 1 is passed through the lower chambers 4b of the support frames 4 while it is supported by the support rollers 6 in the lower chambers 4b, as described above, and while the side ends overlapped each other are situated in the bottom of the tubular belt 1. The tubular belt 1 is then gradually opened again via another guide roller, and the opened belt 1 is returned to the lower roller 3.
This kind of belt conveyer is sometimes extended to a long length such as some hundreds of meter. When the distance between the upper and the lower rollers 2 and 3 is long, especially such a long length, the tubular belt 1 is often twisted around its axis according to the following causes:
(a) a partial or deformed abrasion of the mechanical members and so forth by a long time of use;
(b) a disorder of positions of the support rollers;
(c) an accuracy error of manufacture of the support rollers and their support members;
(d) a partial or deformed abrasion of the support rollers; and
(e) an irregularity of thickness, elasticity, hardness, and so forth of the flexible tubular belt.
Especially, the twist of the tubular belt 1 in the moving path 1a causes a spillover of the bulk material 10 enclosed therein, and imparts excessive forces to the belt 1 and a drive motor, thereby accelerating and abrasions and damages of them greatly.